1. Field of Invention
The present invention relates to a mold making system and a mold making method thereof, and more particularly to a mold making system and a mold making method for making a three-dimensional (3D) micro/nanometer structure on a surface of a roller mold.
2. Related Art
The imprint technology is one of the simplest methods in the technologies for duplicating microelectronic element structures. In this technology, a mold is usually pressed in a material, and the material is then shaped by using an ultraviolet light exposure or heat treatment method. Compared with conventional ultraviolet light exposure methods adopted in most microelectronic technologies, the imprint technology not only can duplicate patterns in a plane direction, but also can imprint structures of steps and contour lines in a vertical direction. In a common imprint technology, the roller imprint and plane imprint modes are adopted. In the roller imprint mode, the roller mold rolls on a substrate to transfer patterns on the mold onto the material on the surface of the substrate. In the plane imprint mode, the patterns on the plane mold are directly transferred onto the material on the surface of the substrate by the plane mold in a surface contact mode. Compared with the plane imprint, the roller imprint mode is advantageous in continuous imprint process; therefore, the roller imprint mode takes advantages in a large-area or continuous imprint process, as well as low cost, low equipment cost, low power consumption, and high production capacity.
As discussed above, in view of the importance of the imprint technology for the development of the next generation industry, the improvement of a roller mold having a micro/nanometer pattern is always a focus of all fields. Conventionally, micro/nanometer patterns can be made on a surface of the roller mold through ultra-precision processing, photolithographic processing, and conventional laser processing. However, the conventional modes have respective disadvantages. For example, the precision of the ultra-precision processing is limited by the size of the machining tool, and as the ultra-precision processing is physical contact processing, the tool might be easily deformed. The photolithographic processing is only used for specific substrates, but the sizes of which are limited. In addition, in the conventional laser processing, due to the use of the continuous wave laser or long wavelength laser mode, a large amount of heat energy cannot be dissipated, such that a thermal diffusion phenomenon occurs in the laser focus area, thus residual thermal stress is generated in the substrate.
In the field of ultra-precision manufacturing technology, high precision and high efficiency processing of ultrafast lasers having ultrashort pulses have promising prospect. The ultrafast laser is also referred to as the femtosecond laser. A pulse period of the femtosecond laser is about 5×10−15 second, so that the femtosecond laser can be widely applied to the biomedical, engineering, and micro-electro-mechanics related fields. Compared with the conventional laser, the advantage of the femtosecond laser is that the ultrashort pulse width and instant heating of the femtosecond laser enable the heat after processing to be dissipated right away, so as to avoid the problem of residual thermal stress due to thermal diffusion.
The femtosecond laser of the near infrared light is highly transmissive for polymer materials, so that the femtosecond laser can pass through photoresist material and be focused in a photoresist material. As the instantaneous light intensity at the focus point is very high, the photoresist material at the focus point can realize nonlinear two-photon absorption which results in photopolymerization reaction. The intensity of the incident femtosecond laser can be suitably controlled to make the light intensity on the optical path insufficient to generate the two-photon absorption effect. Therefore, the photopolymerization reaction only occurs on the photoresist material at the focus point. In the mode above, the femtosecond laser can directly form a microstructure having a specified shape. Compared with the conventional process technology such as lithography etching or electron beam etching, the two-photon absorption mode has the advantages such as mask free, a single step, and a real 3D structure.
Currently, the ultrafast laser or femtosecond laser is used for making a micro/nanometer structure on a surface of a mold only for processing the plane mold, but not for processing the roller mold. In addition to the above thermal diffusion effect in the roller mold, the conventional laser also has difficulties in making verticality and flatness for complicated patterns.